MCQs

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Overall MCQs for Reference

Which of the following best defines a relational database?
a. A collection of tables with relationships
b. A single flat file storing data
c. An array of objects
d. A program for data visualization
Answer: a. A collection of tables with relationshipssanfoundry+2
In a relational database, a row is also called a:
a. Attribute
b. Tuple
c. Field
d. Key
Answer: b. Tuplescribd+1
Which is the term used to refer to a column in a table?
a. Attribute
b. Tuple
c. Row
d. Entry
Answer: a. Attributeknowledgeboat+1
The primary key in a table is used to:
a. Store duplicate records
b. Uniquely identify a record
c. Define the data type
d. Link with external files
Answer: b. Uniquely identify a recordccbp+1
Which SQL statement retrieves data from a table?
a. SELECT
b. INSERT
c. UPDATE
d. DELETE
Answer: a. SELECTsanfoundry+1
To remove a table from a database, use the command:
a. DELETE
b. DROP
c. REMOVE
d. TRUNCATE
Answer: b. DROPplacementpreparation+1
A foreign key in a relational database is used to:
a. Store calculations
b. Reference another table
c. Encrypt data
d. De-duplicate values
Answer: b. Reference another tabletestbook+1
Which of the following is NOT a type of relationship in a relational database?
a. One-to-One
b. One-to-Many
c. Many-to-Many
d. Many-to-One
Answer: d. Many-to-Oneccbp
An index in a database is primarily used to:
a. Store images
b. Speed up searches
c. Link tables
d. Remove duplicates
Answer: b. Speed up searchessanfoundry+1
Normalization is used in relational databases to:
a. Avoid data redundancy
b. Increase data redundancy
c. Prevent foreign keys
d. Change user permissions
Answer: a. Avoid data redundancyknowledgeboat+1
Which constraint ensures that data in a column is unique?
a. FOREIGN KEY
b. UNIQUE
c. DEFAULT
d. CHECK
Answer: b. UNIQUEplacementpreparation+1
What is the process of combining two tables based on a related column called?
a. Union
b. Merge
c. Join
d. Include
Answer: c. Joingeeksforgeeks+1
The union operator in SQL returns:
a. Only distinct rows from both queries
b. Only rows present in both queries
c. Only duplicate rows
d. Only rows present in the first query
Answer: a. Only distinct rows from both queriesscribd
Data stored in tables in a relational database is structured as:
a. Lists
b. Trees
c. Rows and columns
d. Unordered sets
Answer: c. Rows and columnsgeeksforgeeks+1
Which data type is commonly used to store strings in relational databases?
a. CHAR or VARCHAR
b. INT
c. FLOAT
d. BLOB
Answer: a. CHAR or VARCHARgeeksforgeeks
The term “schema” refers to:
a. The set of tables and relationships in a database
b. Only one table
c. Only column names
d. User permissions
Answer: a. The set of tables and relationships in a databasesanfoundry+1
Which command is used to remove all rows from a table but keep its structure?
a. DROP
b. DELETE
c. TRUNCATE
d. REMOVE
Answer: c. TRUNCATEccbp+1
The default sorting order of the ORDER BY clause in SQL is:
a. Ascending
b. Descending
c. Random
d. Based on Primary Key
Answer: a. Ascendingsanfoundry+1
Structured Query Language (SQL) is used for:
a. Managing relational databases
b. Web development
c. Image processing
d. Spreadsheet operations
Answer: a. Managing relational databasesknowledgeboat+1
A candidate key is:
a. Always a super key
b. Never a primary key
c. Composite only
d. Used for data validation
Answer: a. Always a super keytestbook+1
The command to add a new row to a table is:
a. INSERT
b. ADD
c. UPDATE
d. APPEND
Answer: a. INSERTsanfoundry+1
Which constraint prevents null values in a column?
a. UNIQUE
b. PRIMARY KEY
c. NOT NULL
d. FOREIGN KEY
Answer: c. NOT NULLplacementpreparation+1
What is a view in relational databases?
a. A virtual table
b. A schema
c. A physical table
d. An index
Answer: a. A virtual tableknowledgeboat+1
Entity Integrity in a relational database is maintained by:
a. Foreign Key
b. Primary Key
c. Unique Key
d. Index
Answer: b. Primary Keyplacementpreparation+1
To update existing record data, which SQL statement is used?
a. UPDATE
b. MODIFY
c. CHANGE
d. ALTER
Answer: a. UPDATEsanfoundry+1
Referential integrity ensures:
a. Correct referencing between tables
b. That each table has only one row
c. No primary keys
d. Automatic deletion of all tables
Answer: a. Correct referencing between tablestestbook+1
A relation in a relational database is:
a. A table
b. A row
c. A function
d. An index
Answer: a. A tablesanfoundry+1
The JOIN operation merges:
a. Columns
b. Rows
c. Tuples
d. Tables based on related fields
Answer: d. Tables based on related fieldsscribd+1
Which normal form eliminates partial dependency?
a. 1NF
b. 2NF
c. 3NF
d. BCNF
Answer: b. 2NFknowledgeboat+1
A composite key is formed by:
a. A single attribute
b. More than one attribute
c. Only primary key
d. User roles
Answer: b. More than one attributeplacementpreparation+1
SQL command to change an existing value in a column is:
a. UPDATE
b. ALTER
c. MODIFY
d. INSERT
Answer: a. UPDATEccbp+1
A super key is:
a. Any key
b. A set of attributes to identify rows uniquely
c. Only a single column
d. An index
Answer: b. A set of attributes to identify rows uniquelytestbook+1
The result of a cross join is:
a. Cartesian product
b. A union
c. A difference
d. A reference
Answer: a. Cartesian productgeeksforgeeks+1
In SQL, which clause is used to filter the results of a query?
a. WHERE
b. ORDER BY
c. HAVING
d. LIMIT
Answer: a. WHEREsanfoundry+1
Which integrity constraint requires that every value in a foreign key must exist in the referenced primary key?
a. Entity integrity
b. Domain integrity
c. Referential integrity
d. User integrity
Answer: c. Referential integritytestbook+1
The process of ensuring consistency among data is known as:
a. Concurrency control
b. Normalization
c. Data auditing
d. Indexing
Answer: a. Concurrency controlccbp+1
Which operation returns only rows that appear in both result sets?
a. UNION
b. INTERSECT
c. EXCEPT
d. SELECT
Answer: b. INTERSECTscribd
Which SQL keyword is used to restrict the number of rows returned by a query?
a. LIMIT
b. STOP
c. END
d. ROWS
Answer: a. LIMITgeeksforgeeks+1
A relational database structure allows:
a. No relationships
b. One-to-one, one-to-many, and many-to-many relationships
c. Only one-to-one relationships
d. No primary keys
Answer: b. One-to-one, one-to-many, and many-to-many relationshipsccbp+1
Which of the following is a DDL (Data Definition Language) command?
a. SELECT
b. INSERT
c. CREATE
d. UPDATE
Answer: c. CREATEccbp+1
Which clause is used with GROUP BY to filter grouped rows?
a. WHERE
b. HAVING
c. LIMIT
d. ORDER BY
Answer: b. HAVINGplacementpreparation+1
To change the structure of a table, such as adding a column, use:
a. ALTER
b. UPDATE
c. MODIFY
d. DROP
Answer: a. ALTERsanfoundry+1
A record in relational databases is also known as:
a. Field
b. Tuple
c. Attribute
d. Schema
Answer: b. Tuplesanfoundry+1
Which of these is NOT a valid SQL data type?
a. CHAR
b. INT
c. IMAGE
d. PICTURE
Answer: d. PICTUREgeeksforgeeks
The minimum number of tables required to join data is:
a. 0
b. 1
c. 2
d. 3
Answer: c. 2geeksforgeeks+1
Entity-Relationship (ER) modeling is used to:
a. Model database structure
b. Format hard drives
c. Design web pages
d. Encrypt data
Answer: a. Model database structureknowledgeboat+1
Which SQL command updates schema or metadata, not data?
a. ALTER
b. SELECT
c. UPDATE
d. DELETE
Answer: a. ALTERsanfoundry
To extract a subset of a table’s columns, the best SQL operation is:
a. Projection
b. Selection
c. Intersection
d. Merge
Answer: a. Projectionknowledgeboat+1
The main advantage of using relational databases in data science is:
a. Data redundancy
b. Scalability and structured querying
c. Non-standardized data
d. Lack of security
Answer: b. Scalability and structured queryingplacementpreparation+1
The main component of a relational database that allows for establishing relationships between tables is:
a. Field
b. Foreign key
c. Index
d. Attribute
Answer: b. Foreign keytestbook+1

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